Dynamo-electric machine.



J. G. MAGPARLANE & H. BURGB. DNAMo BLEOTBIGWMAGHINE.

APJPLITION FILED APB., 5, 1909.

1,035,717. Patented A ug. 13, 1912.

' Flo. 1.

lll/Claw brush to the positive main brush.

"UFUTED STATES QFFICE.

JAMES COLQUHOUN MILCFARLANE .l-IB ILARRY BURGE, OF C-IELMSFORD, ENGLAND' ASSIGNORS TO THE FIRM 0F CROMPTON AND COMPANY LIMITED, OF ARC WORKS.

'CIiELT/ISFORD, ENGLAND.

DYNAIvIQ-ELECTRIC MACHINE.

l ASupeeicrattm of Letters Patent. Patented A110. 13.1912;

Application leipil 5., i909. Serial No. 488,043.

vided into a motor partv and a generator part (or multiples thereof) by a pair of auxiliary brushes such as are hereafterreerred to, along a plane (or planes) which passes through the said brushes, and a lield magnet also dividedY into a motor part and a generator part, each part being provided with independent windings.

lVe have hereinafter described our invention for simplicity in connection with 'a two- -pole magnetic field.

If two brushes, -hereinafter called for convenience the positive and negative main brushes, are plabed in the ordinary neutral4 position, and are supplied with-a constantlpotential dili'erence, and if the field magnets are provided with suitable windings in the ordinary way, the armature will revolvo at a delinite speed, depending on well known conditions, and there will be a grad ual rise of potential all around both 'sides of the cominutator from the negative main lt' now two further brushes, hereinafter called for convenience the auxiliary brushes, are made to bear on opposite sides oi the comnnitatm at points approximately equi-distant from one of the main brushes, these two brushes will pick up approximately the'same potential. If these brushes are joined together bymeans of a low resistance conductor, there will be practically no circulating current flowing between the brushes on no load. The potential that the-alixiliary brushes will pickup will depend on their distance from the negative main brush, the potential of l, hich for convenience is considered zero, so ,hat by placing the auxiliary brushes .at any ,hilui-distant peints ou the commutator from thenegative mpin brush they may b e made topick up any potential from approxmiately 'zeno-to approximately the potential of the `through the auxiliary brushes.

positive main brush.l -.T he armature ofsuch" a .machine may be considered to be divided 'into two parts along a plane which passes through the auxiliarybrushes and is parallel to the axis of the armature shaft. The, part between the plane passingthrough the auxiliary brushes andv the' positive main Vbrush maybe considered the motor part of the armature, and the part between the -plane passing through the auxiliary brushes and the-negative main brush may be considered the generator part of the armature.

The potential difference induced in vthe lgenerator part' of the armature, fi. e. between vthe negative main brush and the auxiliary brushes is proportional to the number of conductors lyin on' the armature between tlie negative mam b r sh and the plane passing through the auXi iary brushes, and also to the quantity of magnetism ormagnetie.

flux, passing through the surface of the armature from the magnet poles, lhereinafter called the generato'rpoles, between the negative main brush and the plane passing Similarly the potential difference generated in the mo-4 tor part or' the armature, z'. e. between the plane passing through the auxiliary brushes and the positive main brush, is proportional to the number of conductors on the armature surface between the said plane and the positive main brush, and also to the quantity of magnetism, or magnetic flux, passing through the armature surface' from the mag? net poles, hereinafter called the motor poles,

between the said plane and the positive main brush. In order, therefore, to varyV the po-l tential dillerence (hereinafter called the .stcondary potential difference) between the negative main brush and the auxiliary brushes, withoutaltering. the position of the auxiliary brushes on the commutator, it will be necessaryv to alter the relative values of magnetic llux passing through the sur- `face, of thearmature on either side of the plane passing through the auxiliary brushes.

"This cannot be conveniently done without dividing each of the poles into two distinct parts,'and providin each part with independent windings, t e M. M. l". of which can be adjusted independently, either automatically .or otherwise, to give the required values of magnetic flux on each side of the aforesaid plane. It is of no use-altering4v` the relative values of magnet-ic flux on either side of the aforesaid plane, in order to Vary the secondary potential difference, unless a machine of th1s type is provided with a ring armature (that is to say an armature in which the conductors return to the cQmInutator from the backend of the armature without cutting any magne'c flux) because if such a machine is Provided with an ordinary drum wound armature, although the relative quantities of magnetism on either side of the aforesaid plane were changed, this could have no effect on the value of this secondary potential dit-A 'rvlence, l

In a machine constructed in accordance with the principles set forth above', which may ,not only have the poles divided as del scribed, but which may also have the magnetic circuit of the motor poles entirely isolated :from the magnetic circuit of the generator poles. which are provided with equal M. M. FLs, if a current be drawn from the secondary side of the machine, thatis from between the negative main brushand the auxiliary brushes at a very small ditt'ercnce of potential, that is, if the ratio of conversion is large, which effect is obtained by reducing the M. M. F. on each generator pole equally, there will be. a large circulating current flowing between the auxiliary brushes due to the want of balance in the armature. This'want'of balance vis caused by the fact that the current is the lower half of the armature is larger than in the upper halt. This produces an unbalanced M. M. F. in the wiring-l of the armature which t causes a current to vflow in' the conductor,

v `ioining the auxiliary brushes. This circu-v lating current will be diminished as the potential difference on the secondary side is increased, by increasing the M. M. F. uniformly on the generator poles, although the current on the secondary Yside remains constant, and it will finally disappear when the secondary potential difference has attained a definite value. It the secondary potential difference is increased beyond this value, the direction of the circulating current will be changed, z'. e. it will flow in the opposite direction across the auxiliary brushes. This circulating current. is due to armature reaction for, if when the machine is on load and the potential diference in the secondary is small, the current in the generator part of t-he armature must he large compared with the current in the motor part of the armature. The M. M. F. of the generator partof thc armature may therefore be considerably greater than the M. M. F. of the motor part of the armature.

These M. M. F.s are acting'in opposition to one another, and their resultant when superimposed on the field system opposes the M. M. F. of the motor pole and helps the Alating current, it its magnitude and direc- Then the M. M. l1. of the motor part of the armature is greater than that ot the generator part, the circulating current wlll flow 1n the opposite direction. This circution are not properly controlled, is objectionable for the following reasonsz-L It causes the speed oit the armature'to vary between wide limits. i?. It will. under certain circumstances, cause sparking at one or other of the auxiliary brushes. ltrvfill,V under certain circumstances, tend to prevent the desired relation between current and potential ditilei'ence heilig obtained from the secondary side. 4. It will, under certain circlnnstances, tend to make the machine race dangerously. If properly regulated, this .circulating current can he used to ad- Y lvantage as follows :-1. To control the speed. 2. To prevent-'sparking at either of the auxiliary brushes. 3. 'loassist in giv- 'ing the desired relationship between the sec- -lnately constant current, and at the seine ondary current and 'the secondary potential ditl'erenee. 4. To prevent dangerous racing.

lf the machine is constructed with the 1 magnetic circuit of the motor part magnetically connected to the magnetic circuit'of the generator part, the results obtained are substantially the same. There is therefore, no particular bene-tit to be derived from magnetically isolating the motor part of the magnetic circuitfrom the generator part of the magnetic circuit.

By the aid ot our invention we are able to malte a machine constructed as. above, 1 whether having or not having the magnetic circuit of the motor part ot' the machine isolated from the magnetic circuit ot' the generator part; of the machine. supply from its secondary terminals an approximatelyy constant current at a varying potential ditferencc, it provided with suitable windings hereinafter described. v

The objects of this invention are theretore to provide in a machine of the. kind described: A. Means capable. of regulating and governing the value of the circulah ingr current between the auxiliary brushes, and at the same time producing a droop in the secondary potential di'tl'creuce as the secondary current increases. l. As a modification of the above, m aus for producing an automatically varying potential ditl'crence in the secondary with approxi-y maar@ tiene regulating and governing the circulating'current in order to produce under these circumstances the desired results. The meansv provided for carrying out these objects are particularly described by reference to the diagrams in the accompanying drawings.

chine inwhich the generator poles are provided with a series winding serving as a conductor between the auxiliary brushes; and Fig. 2 shows diagrammatically the ad-l dition to the machine shown in Fig. 1 ot shunt windings upon the generator poles.

Referring to Fig. 1 it will be observedtha't the machine is provided with three terminals X,-Y, and Z.

N and S are the motor poles and a and s are thel generator poles of the machine.

a and Z) are the main brushes connected respectively to the terminals X and Z, and 0. and d are the auxiliary brushes joined by a conductor which is connected by a second conductor to the terminal Y of the machine.

X and Z arethe term-inalsoi'the primary circuit and Y and Z are the terminals ot the secondary circuit, the terminal Z being common to boththe primary and secondary cirrlhe generator poles a and s are each provided with a seriesl winding A1, A2, respectively, connected in series with and forming the conductor joining the auxiliary brushes c and 6l, the connection to the terminal Y ot the secondary circuit being made at the point c, as shown. in Fig. 1, midway between the windings 'A1 and A2.

The motor poles N S are provided with l shunt windings D1, D2 respectively, and the J regulators generator poles a, s, areprovided with similar 'windings D3, D", shunt lield regulators R1, R2, being arranged in series with said shunt windings D1, D2, and D3, D4, respec- By manipulating the shunt field R1, it, the iii. ivi. i?. of the windings D1, D2 and D3, D* can be adjusted independently as will be well understood, to give the required values oit magnet-ic flux on each side of the plane passing through the auxiliary brushes. Thus, in the action of the machine, a current flows 'from both brushes c, d, outward to the terminal Y, passing through the series coils A1, A? in such direction as to oppose the normal shunt ilux, thereby reducing the secondary voltage in proportion to the load. When, however, the armature is out of balance, as already described, an additional current flows out of one brush and into the otherthrough the coils A,A2,thus strengthening one pole and weakening the other and thereby tending to restore the magnetic balance of the armature.

As shown in Fig. 1 the series windings not only prevent circulatmg ,currents from Figure 1 shows diagrammatically a ma passing between the auxiliary brushes, but produce a droop in the secondary lvoltage as the secondary current increases.

Referring to Fig. 2, a machine similar to that described with reference to Fig. 1 is shown, but instead ofthe plain shunt windings D3 and D4, we employ la winding B on one generator pole 'n and a shunt winding C on the other generator pole s, the motor shunt windings D1 and D2 being connected between the main brush a and the auxiliary brushes o and (Z or in any. other suitable manner. The action of these windings depends on the tact that the magnetization produced by the winding B remains constant, while the magnetization produced by the winding C depends upon the voltage across the terminals Y, Z. Thus with a large ratio of transformation which, as Aalready described, throws the armature out of balance, a weakening of the pole s occurs which actually restores the magnetic balance ot the armature. additional advantage in that on short circuit, the voltage across Y, Z diminishes practically to Zero and the flux produced by the coil C is therefore largely reduced. `The total tlux'through the generator side of the armature is thus correspondingly reduced and the current in the secondary circuit can never attain an excessive v alue.

These` windings vhave an Y In operation the terminals X, Z are connected to the source of supply and the terminals Y, Z are connected to the arc lamp or other load which requires to be :ted with constant current irrespective ot' the resistance in the circuit.

As stated above there are three external terminals in the machine, one, Y, connected to the terminal of the auxiliary brushes c and el, one, X, connected to one ordinary brush a, and one, Z, connected to the other ordinary brush o. It' any two terminals are selected for the purpose o' supplying the motor current, the generator current may be taken between either of-these and the third terminal. Hence it is immaterial how the connectionsof the primary and secondary circuits are made to the brushes, as is also thecase with an ordinary motor generator, and consequently, it will be seen that motor current can be taken in between any two conductors and transformed current can be delivered between one of these and the third conductor.

It is to be understood that the invention is also applicable to machines ot the multipolar type, and to these machines', as well as two pole machines, when fitted with commutating poles. A

Having described our invention, what we claim, and desire to secure by Letters Patent is 1. A dynamo electric machine comprising a, single ring armature, eld magnets, said field magnets being isolated magnetically from each other, thereby dividing the field into a motor portion and a generator portion, three external terminals to said machine, a pair of main brushes each connected to one of said terminals, a pair of auxiliary brushes, a conductor Wound-as a series Winding around the poles constituting said generator portion of said machine and joining the said pair of auxiliary brushes, and a connection between the middle point of said condilctor and the third terminal of the ma chine. y t

2. A dynamo electric machine comprising a single ring armature, field magnets, said field magnets being isolated magnetically from each other, thereby dividing the field into a motor portion and a generator portion, three external terminals to said machine, tWo of said terminals being primary terminals, the third terminal being a secondary terminal, and one of said primary terminals being commento primary and secondary, a pair of main brushes each connected to one of said primary terminals, a pair oii'auxiliary brushes, a conductor Wound as a series winding around the'poles constituting said generator portion of said `machine and joining said pair of auxiliary brushes, the middle point of said conductor together with said common ter .iinal forming the. secondary terminals of the machine, and a shunt winding on one generator pole connected across the primary terminals and a shunt winding around the other generator pole connected across the secondary ter1ninals. Y

In testimony whereof We have hereunto set our hands in presence of two subscribing Witnesses.

JAMES GOLQUHOUN MACFARLANE. HARRY BURGE.

`Witnesses:

ERNEST JOHN HILL, HARRY J. SToPEN.

Uopies of this patent may be obtained for ve cents each, by addressing the Commissioner of Patents.

Washington, D. GJ 

